1. Field of the Invention
The present invention is directed toward an improved vehicle brake caliper assembly and, more particularly, toward an improved caliper abutment plate.
2. Description of Related Art
With reference to FIGS. 6-7, a known brake caliper assembly generally includes a caliper housing 20, a pair of brake pads 22, and a mounting assembly for movably mounting the brake pads in the caliper housing 20. In FIGS. 6 and 7, only one half of the caliper housing is illustrated, with it being understood that the other half of the caliper housing is functionally identical. The caliper housing 20 includes one or more pistons (not shown) that receive pressurized brake fluid, typically from the brake master cylinder, and are driven to move toward and away from the backing plate on a rear side of the brake pads 22.
The brake pads 22 are mounted in opposition to one another and on opposite sides of the brake rotor (not shown). The brake pads 22 include a front friction material, and a rear backing plate. Generally, the front friction material is bonded to or otherwise attached to the rear backing plate, and the rear backing plate extends so as to define the peripheral surface of the brake pads. Upon actuation/deactuation of the associated piston(s), the brake pads 22 move relatively toward and away from one another and, in so doing, the friction material on the front of the brake pads 22 is brought into and out of engagement with the brake rotor disposed therebetween.
The brake pad mounting assembly can take many forms. In one form, two or more rods 24 extend between opposite sides of the caliper housing, and the two or more rods 24 extend through associated openings formed in the brake pads 22. The rods 24 also resiliently receive a mounting clip (not shown) that helps to properly position and retain the brake pads 22 in place on the caliper housing 20.
In practice, the inner surface of the caliper housing 20 has a recessed portion 26 in which the brake pads are received. The recessed portion 26 is shaped and sized such that the brake pads 22 (i.e., the front surface of the friction material) are normally generally flush with an interior surface 30 of the caliper housing, and move outwardly so as to project from the interior surface 30 of the caliper housing 20 under the influence of the pistons. Thus, the recessed portion 26 is defined by a rear wall 26a and a pair of end walls 26b, with the pistons extending through the rear wall and toward the backing plate on the rear surface of the associated brake pad 22. The end walls 26b defining the recessed portion 26 of the caliper housing are adjacent to, but spaced slightly from, end surfaces 22a of the brake pad 22. The end surfaces 22a are provided by the backing plate, which extends outwardly from the friction material so as to define the peripheral surface of the brake pad 22, as described hereinbefore. The top and bottom surfaces of the brake pad 22 are generally exposed, although this is not mandatory.
The backing plate at the rear surface of the brake pad 22 is engaged by the caliper pistons, as described hereinbefore. The backing plate end surfaces 22a face toward the associated end walls 26b of the caliper housing recessed portion 26. The caliper housing end walls 26b and brake pad 22 are typically spaced a short distance from one another, the brake pad backing plate and caliper housing are commonly formed from different metals and may tend to corrode over time. For example, the caliper housing is normally formed from a light, relatively soft material, such as aluminum, aluminum alloys, or magnesium alloys, whereas the brake pad backing plate is conventionally formed from a hard, durable material, such as steel.
During braking the backing plate end surfaces 22a engage the end walls 26b of the caliper housing 20. It is believe that torque forces are generated on the brake pad 22 when the brake pad friction material engages the spinning brake rotor, and that these torque forces are transferred to the caliper housing 20 when the backing plate end surfaces 22a contact the caliper housing end walls 26b. Unfortunately, since the caliper housing 20 is conventionally formed from a relatively softer material than the brake pad backing plate, engagement between the backing plate and the caliper housing may wear or deform the relatively softer caliper housing end walls 26b. 
In response to these problems, it is known in the art to attach a thin abutment plate 28 to the caliper housing end walls 26b that face toward the brake pad end surfaces 22a so as to receive the backing plate during braking. The known abutment plate 28, which is illustrated best in FIGS. 8 and 9, includes a thin plate-like body 28a and a centrally disposed mounting tab 28b. To accommodate the abutment plate 28, the end walls 26b of the of the caliper housing recessed portion 26 have an angled notch 26c formed therein that is adapted to receive the abutment plate mounting tab 28b. The angled notch 26c defines a planar surface that is at an acute angle to the planar surface of the end wall 26b, preferably at an angle of about 45°.
The abutment plate body 28a is generally planar and u-shaped, and configured to be disposed in a face-to-face manner over the associated surface of the caliper housing end wall 26b. As such, the plate body 28a extends over the caliper housing end wall 26b, and has a length generally equal to a length of the brake pad ends 22a and a width generally equal to a width of the caliper housing end wall 26b and the brake pad thickness. The mounting tab 28b is integrally formed with the plate body 28a, and bent out of the plane of the plate body 28a so as to be secured to the mounting surface that is provided by the notched surface 26c formed in the caliper housing end wall 26b. Preferably, a screw 32 is inserted through a hole 28c formed in the mounting tab 28b and threaded into a tapped hole extending through the angled notch 26c of the end wall 26b so as to secure the abutment plate 28 to the caliper housing 20.
This arrangement works well in preventing contact between the brake pad end surfaces 22a and the caliper housing 20. However, it has been found to be rather noisy. In this regard it is important to note that the abutment plate 28 is thin, lacks substantial mass, and is only positively secured to the caliper housing end wall 26b at the mounting tab 28b, which itself is only connected to the abutment plate body 28a at the upper end of the tab.
It is believed that, in use, ends 28d of the abutment plate body 28a may become warped or otherwise displaced from firm engagement with the caliper housing end walls 26 and, upon application of the brakes, may chatter or repeatedly engage and disengage with the caliper housing 20, creating a disturbing noise that is objectionable to the operator. It is believed that one reason for this possible distortion of the abutment plate 28 is that the abutment plate is relatively thin, has low stiffness, and is not robust enough to provide a stable engagement surface to receive the brake pad backing plate end surfaces 22a. It is also believed that the abutment plate may distort since the plate is only secured to the caliper housing 20 via the screw connection of the mounting tab 28b at the mid-portion of the abutment plate body 28a, while the ends 28d of the abutment plate body 28a are not positively secured to the caliper housing 20. In this regard it is thought that having the mounting tab 28b separated from the abutment plate body 28a and bent out of the plane of the abutment plate body 28a weakens the support or attachment that the mounting tab 28b provides to the abutment plate 28, especially the ends 28d of the abutment plate 28, and allows the abutment plate body 28a to warp or bend over time.
Accordingly, there exists a need in the art for an improved structure that avoids or minimizes the problems found in the prior art.